This invention pertains generally to explosive and ignitive devices and, more particularly, to a low energy fuse for use in transmitting shock waves.
Low energy fuses are employed in aerospace and other applications for transferring an explosive signal from one location to another and in providing precise delays or timing relationships between different energetic reactions which are initiated by the explosive signal. Examples of such fuses are found in U.S. Pat. Nos. 3,590,739, 4,290,366, 4,328,753, 5,048,420, 5,166,470, 5,317,974 and 5,844,322.
These low energy fuses typically consist of a hollow plastic tube with a reactive material distributed along the length of the tube for sustaining a shock wave. The reactive material is commonly in a pulverulent or powdered form and is coated onto the inner wall or surface of the tube. The tube must have sufficient strength to avoid collapse or other damage prior to rapid deflagration, and to remain intact during use. There must also be proper adhesion between the tube and the powder so that the powder will remain in place on the wall of the tube.
Heretofore, there have been some attempts to provide both strength and adhesion by the use of laminated plastic tubes comprising an inner layer with good adhesion properties and an outer layer which provides mechanical strength and reinforcement. An example of this laminated structure is found in U.S. Pat. No. 4,328,753.
Other fuses have employed a single ply plastic tube with an adhesion enhancer. U.S. Pat. No. 5,317,974, for example, discloses a single ply tube which is fabricated of a draw orientable polymer resin with a modifier in the extrusion melt for imparting an improved powder retaining capability to the tube.
It is in general an object of the invention to provide a new and improved low energy fuse for transmitting shock waves.
Another object of the invention is to provide a low energy fuse of the above character which has improved adhesion properties for the reactive powder coating that is distributed along the length of the fuse.
These and other objects are achieved in accordance with the invention by providing a low energy fuse having a hollow plastic tube fabricated of an ethylene-chlorotrifluoroethylene terpolymer, with a coating of reactive powder on an inner wall of the tube. The terpolymer contains a third polymer which enhances adhesion of the powder to the tube, and in the disclosed embodiment, the third polymer is hexafluoroisobutylene.